井周速度變化時(shí)的散射波特征研究
本文關(guān)鍵詞：井周速度變化時(shí)的散射波特征研究 出處：《中國(guó)石油大學(xué)(華東)》2015年碩士論文 論文類型：學(xué)位論文
更多相關(guān)文章： 散射波 Born近似 測(cè)井?dāng)?shù)據(jù)反演 聲速?gòu)较虺上?/b>
【摘要】：實(shí)際測(cè)井中經(jīng)常遇到鉆井機(jī)械碰撞、地層應(yīng)力釋放、鉆井流體侵蝕或者頁(yè)巖粘土膨脹等現(xiàn)象,這都會(huì)造成井壁附近地層參數(shù)的變化,進(jìn)而導(dǎo)致井壁附近的地層彈性波速度與遠(yuǎn)離井壁處的速度相比相差很多。為了研宄該地層中井壁附近的速度變化情況,本文介紹了一種利用單極縱波提取散射波信息反演地層徑向縱波速度剖面的層析成像方法,該方法能夠利用散射波的變化特征重建地層徑向縱波速度變化,它對(duì)評(píng)價(jià)井壁穩(wěn)定性、估算地應(yīng)力、探測(cè)流體侵入、優(yōu)化油藏生產(chǎn)等都有著重要的意義。本文將在地震勘探領(lǐng)域已經(jīng)獲得廣泛應(yīng)用的彈性波散射理論應(yīng)用到聲波測(cè)井領(lǐng)域。構(gòu)建了合適的聲速擾動(dòng)模型,將弱非均勻介質(zhì)中根據(jù)Born近似獲得的散射波積分表達(dá)式在柱坐標(biāo)先展開(kāi),針對(duì)平面波入射和球面波入射的不同情況,進(jìn)一步理論求解了這兩種情況下的散射波解析表達(dá)式。將地震中常用的Rytov近似與Born近似得到的結(jié)果進(jìn)行對(duì)比,發(fā)現(xiàn),在地震領(lǐng)域內(nèi)適用性更好的Rytov近似并不適合聲波測(cè)井領(lǐng)域,在聲波測(cè)井領(lǐng)域內(nèi),Born近似的使用效果更好。利用理論求解的不同速度擾動(dòng)模型下平面波和球面波分別入射得到的不同的散射波理論表達(dá)式,結(jié)合發(fā)展成熟的有限差分等方法,進(jìn)行井周散射聲場(chǎng)的數(shù)值模擬,分別討論井周徑向和周向地層速度變化情況下的散射波變化特征,結(jié)果表明,在井周徑向和周向速度變化時(shí),散射波均能給出很好的響應(yīng)。尤其是針對(duì)不同周向方位上速度增加或者降低的情況,散射波的相位正負(fù)變化十分明顯。十分有利于速度變化情況的反演。最后,將得到的散射波理論表達(dá)式用于聲波測(cè)井?dāng)?shù)據(jù)反演,分別討論不同目標(biāo)函數(shù),不同聲源入射,不同速度擾動(dòng)模型下的反演情況,根據(jù)不同情況下得到的反演結(jié)果進(jìn)行優(yōu)化選擇,并將之應(yīng)用于現(xiàn)場(chǎng)實(shí)際數(shù)據(jù)的處理,取得了令人滿意的效果。
[Abstract]:Drilling machine collision, formation stress release, drilling fluid erosion or shale clay expansion are often encountered in actual logging, all of which will cause changes in formation parameters near the wellbore. In order to study the variation of formation velocity near the well wall, the elastic wave velocity of formation is much different from the velocity far away from the well wall. In this paper, a tomography method for retrieving the velocity profile of radial longitudinal wave of strata by extracting scattering wave information from unipolar longitudinal wave is introduced. This method can reconstruct the velocity change of radial longitudinal wave of stratum by using the variation characteristic of scattering wave. It can be used to evaluate wellbore stability, estimate in-situ stress and detect fluid intrusion. Optimization of reservoir production is of great significance. In this paper, elastic wave scattering theory, which has been widely used in seismic exploration, has been applied to acoustic logging, and a suitable acoustic disturbance model has been constructed. The integral expression of scattering wave obtained by Born approximation in weakly inhomogeneous medium is first expanded in cylindrical coordinates, aiming at the different cases of plane wave incidence and spherical wave incidence. Furthermore, the analytical expressions of scattering wave in these two cases are solved theoretically, and the results obtained by Rytov approximation and Born approximation are compared and found. Rytov approximation, which has better applicability in seismic field, is not suitable for acoustic logging. The Born approximation is more effective. The different theoretical expressions of scattering wave are obtained by using the different velocity perturbation model solved by the theory of plane wave and spherical wave respectively. Combined with the developed finite difference method, the numerical simulation of the scattering sound field around the well is carried out, and the variation characteristics of the scattering wave in the radial and circumferential formation velocities around the well are discussed, respectively. When the radial and circumferential velocities around the well vary, the scattering wave can give a good response, especially for the different circumferential azimuth increase or decrease of velocity. The positive and negative phase change of scattering wave is very obvious, which is very beneficial to the inversion of velocity change. Finally, the theoretical expression of scattering wave is applied to the inversion of acoustic logging data, and different objective functions are discussed respectively. According to the inversion results obtained under different conditions, the inversion results obtained from different incident sources and different velocity perturbation models are optimized and applied to the processing of field actual data, and the results are satisfactory.
【學(xué)位授予單位】：中國(guó)石油大學(xué)(華東)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P631.81
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